In Canadian Patent Application No. 2,185,076 (U.S. Pat. No. 5,799,632) Easton Bennett disclosed a novel heat exchanger configuration for a motor vehicle exhaust. This heat exchanger had an exhaust pipe with a flow passage formed of a coil of tubing. The exchange medium flows through the coil as hot exhaust gases flow through the flow passage in the centre of the coil.
In Canadian Patent Application No. 2,247,759 (U.S. patent application Ser. No. 09/158,711) Easton Bennett disclosed an improvement to the novel heat exchanger configuration. This heat exchanger had the coil of tubing with the central flow passage positioned in a larger housing, thereby forming an annular flow down the outside of the coil of tubing, in addition to the central flow passage. This configuration proved to be even more efficient for heat transfer.
In some applications, however, there is a concern that the coolant used as exchange medium will become over heated.